The present invention relates to an improved method and system for production of steam for steam injection in oil wells.
Many oil reservoirs contain heavy oil having a viscosity that makes it economically difficult or impossible to produce oil using conventional methods. Large oil reservoirs of this type are located in e.g. Venezuela
The most common methods for recovering heavy, high viscosity oils comprises injection of steam into the reservoir. Steam enhances the production of heavy oil by reducing the viscosity by heating.
According to one method referred to as cyclic steam stimulation (CSS), steam is injected into a well for a period of several days to a few months. The well is then shut down for a period known as the soak period, before well is brought on production for a period. After this production period the same cycle is repeated.
According to another method known as steam drive, steam is injected into some wells dedicated to continuous steam injection at the same time as oil is produced in adjacent wells.
Today, steam for injection into wells is produced by means of gas fired boilers in a centralised unit on the field. The steam, having a temperature of approx. 300.degree. C. and a pressure of about 100 bar, is transported from this unit to the wells by means of high pressure pipelines.
As an example, the area of an oil field may be 600 square km, and may have 40 or more clusters of wells, each cluster typically having approx. 10-50 wells. The investment costs in pipelines and steam generators are therefore substantial. The thermal loss in the pipelines is large.